Abstract: To solve the problem of radar-IFF correlation in back-to-back configuration, an algorithm was discussed, mainly including time-alignment between radar tracks and identification friend or foe(IFF) points, construction of discriminate functions, choice of the decision-making rule, and computation formula of decision thresholds. Moreover, the problem of ambiguity was also discussed. Simulation results in four typical conditions show that, with the greater ratio of target interval to range from target to radar, the better performance is; when it comes to target cross, the closer to the crossing, the worse the correlation is; when target maneuvering, time registration realized by track smoothing better than track predicting, while, in other conditions, the correlation results produced by these two methods are similar. Moreover, the correlation performance obtained in north east down(NED) coordinate system is almost the same as that in polar coordinate system. There, n/m logic should be chosen as 2/3 or 3/4 in order to promise both the missing correlation probability of friendly target and the false correlation probability of unknown target are low.